Morn'in 84Jim,
Well as per neck turning, it never hurts to true up the outside of a case neck and it is better to be safe then sorry.
However, so far this has not been an issue with this decrease in neck dia. and the thin brass found on 30/30s.
When I got my set of Hornady 25/35 dies, one of the customer comments about the dies was about the problems the dies gave when forming 30/30 to 25/35.
After reading his comments, I didn't buy into his "problems" as I had formed enough cases over the years to know a trick or two.
Lube is the key!!!!!!!!!! STP will smooth out about any forming operation, but as already indicated it is a mess to get the cases clean.
It was very likely here on "GB" that I picked up the tip about the Imperial Sizing Wax, and it was a good one. It does work and is easy to wipe off the cases.
Guess looks can be trick a person, as the 30/30 to 25/35 is just one slick pass through the dies, load and shoot.
Take care not to over lube the case, as the thin brass dents very easy.
As indicated, my friend's 25/35 is a Savage model #99 which allows us to use a spitzer style bullet. I loaded the Hornady 100gr. Interlock for his rifle.
Just rec'd word last night that his daughter took a whitetail doe with a high lung shot at about 100yds.
I replyed asking about the bullet, and his answer this morn'in was, no bullet - a complete pass through leaving a good sized exit hole and breaking a rib on the way out.
I figured the Ol'cartridge would have been out of steam, but seems like a good 100yd deer cartridge to me with those results.
Keep em coming!
CDOC